Various closure assemblies have been heretofore suggested for closing and sealing discharge openings in containers which are designed for storing and transporting bulk chemical materials. These containers often have a bottom discharge opening with a sliding gate type closure which permits the contents to be discharged when the gate is open and shut off when the gate is closed. Gates of this type are particularly important since in storing or transporting large volumes of hazardous chemicals, such as powdered sodium hydrosulfite, any escape of the powder poses a serious health problem and potential fire hazard.
U.S. Pat. No. 4,785,966 discloses a slide gate assembly in which elongated cam bars (34) and (36) are used in conjunction with a flexible seal (50) having a yieldable wiper lip (54) which is in contact with the slide gate when the cams are rotated between a first engaged and closed position (FIG. 6) and a second disengaged position (FIG. 7). While slide gates of this type have been used on returnable aluminum container bins for transporting dry chemicals in amounts approximating 4,400 pounds net weight, they suffer from several disadvantages. Due to the heavy weight of the overlying material, it is important to reduce friction on opening and closing the gate as much as possible. In rotating the cam bar, for example, it is necessary for the operator to physically hammer the cam bars to the disengaged position and then, in most instances, use a come-along to pull the slide gate open. Due to the heavy weight and friction the slide gate may suddenly pop open during opening and the operator then becomes at risk from the escaping powder. While gates of this type are acceptable and meet the requirements of DOT 56 specifications, they suffer the disadvantage of not effectively closing the discharge opening when it is closed and not safely opening the slide gate with repeated cycles of opening and closing.